With current perpendicular magnetic recording technology, the magnetic recording areal density has been pushed to around 500˜600 Gb/in2, and has almost reached the physical upper limit imposed by the superparamagnetic effect. Even with the availability of a higher coercivity magnetic material such as FePt and CoPd, a poor writability resulting from saturation of the writing head is expected to become a bottle neck. Energy Assisted Magnetic Recording (EAMR) or Heat Assisted Magnetic Recording (HAMR) technology has become the common pursuit in data storage circle, since the technology offers a way to circumvent the writability bottleneck and further push the data areal density to 1 Tbit/in2 and beyond. The EAMR/HAMR technology can eventually merge with the patterned media.
Near Field Transducer (NFT) is a critical element for an EAMR or HAMR head to transfer enough energy to a tiny bit region and heat the region up to a temperature close to the Currier Temperature temporarily so as to achieve the writability within the short duration. FIG. 1 is a diagram depicting an NFT 102 disposed adjacent to a magnetic pole 104 and having a sloped top cladding 106 comprised of a dielectric material (e.g., an aluminum oxide).
A traditional approach to form such a top cladding having a sloped region (hereinafter referred to as “dielectric slope”) is by a milling or RIE operation which requires a buffer or metal etch stop layer. Typically, such a buffer or metal etch stop layer remains under the dielectric slope after the etching operation. For some optical applications, such as in an EAMR writer, only an optically transparent dielectric material can be used for the buffer or metal etch stop layer, thereby severely limiting the choice of metals and buffer materials that can be used for this purpose.